Serial Numbers start at 1000 and were only introduced in May 2007.
Prior to this date you can identify what MK arm you have by following these guidelines.
Serial No. 1000 – all Silver and above arms post serial no. 1000 have a special damping on the tube – this was a relatively minor enhancement giving more bass depth.
From Serial No. 1023 on 13th June 2007 a packing insert was introduced which prevents damage to the dual pivot bearing if badly dropped in transit.
From Serial No. 1086 a new internal pillar style on Enterprise, and arm tube damping, respectively, were introduced.
From Serial No. 2117 a shatterproof bearing on the MK3 arm was brought in (date: 1-10-2007)